Zero offset numerical servo machine control system

ABSTRACT

A numerical control system for machine tools or the like such as milling machines is disclosed which directs movement by absolute measurement from a reference zero. Programmed data relating to a desired absolute position of the reference zero is entered into a command register, the contents of which is compared bit by bit with data relating to the absolute actual position of the machine tool entered into a position register. The programmed dimension data relates to the actual size of the desired workpiece as provisions are made for entering data relating to tool size offset by means other than the program. A complete system is disclosed including the logic which synchronizes the input of the machine tool actual position with the command position data entered into the system from the programmer as well as the means for controlling the feed speed of the machine tool responsive to programmed data.

United States atent Payne et al. 51 May 23, 1972 s41 ZERO OFFSET NUMERICAL SERVO 3,430,121 2/1969 Yoshitake et al. ..3l8/572 MACHINE CONTROL SYSTEM 3,073,998 1/1963 Bower ..3l8/572 2,933,244 4/1960 Tripp ..3 18/572 X [72] Inventors: Robert A. Payne, Des Plaines; John F. Van

Der Molen, Elmhurst, both of I11. p 1- E Lynch [73] Assignee: Stewart-Warner Corporation, Chicago, Ill. f" Douvas' wllham Newman and on er [22] Filed: Aug. 22, 1969 21 Appl. No.: 852,330 [57] ABSTRACT A numerical control system for machine tools or the like such Related Apphcaflon Data as milling machines is disclosed which directs movement by [63] Continuation f 560322, June 24 1966 absolute measurement from a reference zero. Programmed data relating to a desired absolute position of the reference 52 US. (:1 ..318 572, 318/603 235/151.1 1 m0 is cmmand register, the whid 90/13 is compared bit by bit with data relating to the absolute actual [51] Int. Cl. ..G05b 19/24 position of the machine tool entered into a position register 58 Field of Search ..3l8/572- 235/151.11- 90/13 The Pmgrammed dimensm data dates the size the desired workpiece as provisions are made for entering data 56] References Cited relating to tool size ofiset by means other than the program. A complete system is disclosed including the logic which Nl STATES PATENTS synchronizes the input of the machine tool actual position with the command position data entered into the system from 3,218,532 1 1/1965 TOSCahO "318/572 the programmer as we as the means f controlling the f 3,430,035 2/1969 Read ..3 1 8/572 X speed ofthe machine too] responsive to programmed data 3,327,101 6/1967 Evans ...3l8/572 X 3,340,447 9/1967 MacDonald ..3 18/572 X 11 Claims, 29 Drawing Figures A005 warm/.7 333 /2 2M 201 l "X N 0/2 057' COMMAND KEG/5'75? DOI/WON/fiffi/JTF/E k i @5405? OFFIFI' PM fi //0 Il/fiffiACf YflOa I I H "1 2/0, 1 COMMAND Pia/5m? POI/770W PEG/J7EE I 1 D/BDEZ I 2040 I 1 1 21004-7? 1? m t Pm: mam: (W!!! Fee 20 Patented May 23, 1972 3,665,280

23 Sheets-Sheet 1 y/lgzt gw Af/v azney A 7 r d/may Patented May 23, 1972 (M07426 WWI/30 Fifi/Eff 23 Sheets-Sheet 6 DVD/674704 0/6. 0/5/24 A V mac/170w f/YVENTOPS @WMM Patented May 23, 1972 3,665,280

23 Sheets-Sheet a Patented May 23, 1972 23 Sheets-Sheet 11 "y" AX/S A os/c CONT/80L mam/e Patented May 23, 1972 23 Sheets-Sheet 12 /4 r /a/zney Patented May 23, 1972 3,665,280

25 Sheets-Sheet 1 Patented May 23, 1972 I23 Shaetm-Sheot L5 MN m Patented May 23, 1972 23 Sheets-Sheet 16 Patented May 23, 1972 3,665,280

23 Sheets-Sheet 17 KWHMQ D n K M Kw 6 KM NU 23 Sheets-Sheet 18 Patented May 23, 1972 Patented May 23, 1972 23 Sheets-Sheet 19 

1. For use with a machine having a tool, a workpiece support, and driving means to provide relative movement between said tool and said workpiece support, a control system for said driving means comprising input means for representing a tool offset measurement in BCD code notation, input means for representing a desired relative end position measurement from a reference position in BCD code notation signals and for representing the desired direction of tool offset, means for arithmetically combining said input signals by adding or subtracting in accordance with the tool offset desired direction to provide a tool offset compensated end position signal, means for sequencing said combining means to combine respective significant digits of said BCD input code signals in sequential order, means for comparing said combined signals with the relative position of said tool and workpiece to cause said drive means to provide relative movement to the tool offset compensated end position, said sequencing means causing said combining means to combine the respective significant digits in sequential order from the most significant digit to the least significant digit; and wherein said combining means comprises a multi-bit shift register having a sufficient number of shift stages to store the tool offset and end position measurements in straight binary code notation, a multiplier connected to the output of said shift register having a times two and a times eight output and a two channel input full adder-subtractor circuit having its output connected to the inputs of said shift register; and wherein said sequencing means comprises a first gate for connecting the output of said shift register to one input of said adder, second and third gates for connecting each of said multiplier outputs to a respective one of said adder-subtractor inputs, fourth and fifth gates for connecting each of said measurement inputs to the other input of said adder, and an arithmetic cycle sequencer operative responsive to the input of each significant digit of said BCD code signals to sequentially;
 1. control the opening of said second and third gates to multiply the contents of said register by ten,
 2. control the opening of said first and fourth gates to arithmetically combine the respective digit of one of said BCD measurement input signals with the contents of said register; and
 3. control the opening of said first and fifth gates to arithmetically combine the respective digit of the other of said BCD measurement input signals with the contents of said register.
 2. control the opening of said first and fourth gates to arithmetically combine the respective digit of one of said BCD measurement input signals with the contents of said register; and
 2. The control system of claim 1 wherein said comparing means comprises means for representing the relative positions of said tool and workpiece support in straight binary code notation signals and a full subtractor for comparing said position signals with the combined measurement signals, said driving means being responsive to the output of said subtractor to cause movement to the tool offset compensated end.
 2. control the opening of said first and third gate means to arithmetically combine the respective digit of one of said BCD measurement input signals with the contents of said register, and
 2. control the opening of said first and fourth gates to arithmetically combine the respective digit of one of said BCD measurement input signals with the contents of said register, and
 2. control the opening of said first and fourth gates to arithmetically combine the respective digit of one of said BCD measurement input signals with the contents of said register; and
 3. control the opening of said first and fifth gates to arithmetically combine the respective digit of the other of said BCD measurement input signals with the contents of said register.
 3. control the opening of said first and fifth gates to arithmetically combine the respective digit of the other of said BCD measurement input signals with the contents of said register.
 3. control the opening of said first and fourth gate means to arithmetically combine the respective digit of the other of said BCD measurement input signals with the contents of said register.
 3. The control system of claim 2 wherein said driving means comprises separate motors for providing relative motion in at least two respectively perpendicular directions; and wherein said combining means comprises a second shift register, each register being associated with one of said directions and means for selecting at least one of said registers in accordance with the direction of travel to the compensated end position.
 3. control the opening of said first and fifth gates to arithmetically combine the respective digit of the other of said BCD measurement input signals with the contents of said register.
 4. In combination with a machine having a tool, a workpiece support and driving means for providing relative movement between said tool and workpiece support, a control system for said driving means comprising input means for representing a tool offset measurement in BCD code notation signals, input means for representing a desired relative end position measurement from a reference position in BCD code notation signals and for representing the desired direction of tool offset, means for arithmetically combining said input signals by adding or subtracting in accordance with the desired direction of tool offset to provide a tool offset compensated end position signal, means for sequencing said combining means to combine respective significant digits of said BCD input code signal in sequential order, means for comparing said combined signals with the relative position of said tool and workpiece to cause said drive means to provide relative movement to the tool offset compensated end position, said sequencing means causing said combining means to combine the respective significant digits in sequential order from the most significant digit to the least significant digit; and wherein said combining means comprises a multi-bit shift register having a sufficient number of shift stages to store the tool offset and end position measurements in straight binary code notation, a multiplier connected to the output of said shift register having a times 2 and a times 8 output, and a two channel input full adder-subtractor circuit having its output connected to the inputs of said shift register; and wherein said sequencing means comprises a first gate for connecting the output of said shift register to one input of said adder, second and third gates for connecting each of said multiplier outputs to a respective one of said adder-subtractor inputs, fourth and fifth gates for connecting each of said measurement inputs to the other input of said adder-subtractor, and an arithmetic cycle sequencer operative responsive to the input of each significant digit of said BCD code signals to sequentially:
 5. The combination of claim 4 wherein said end position measurement and tool offset direction inputs comprise a punched tape reader and saiD tool offset measurement input comprises a manually controllable device.
 6. For use with a machine having a tool, a workpiece support, and driving means to provide relative movement between said tool and said workpiece support, a control system for said driving means comprising input means for representing the actual tool size offset measurement in BCD code notation signals, input means for representing a desired relative end position measurement of said tool and workpiece from a reference position in BCD code notation signals and for representing the desired direction of tool size offset, means for arithmetically combining said input measurement signals, means for causing said combining means to add or subtract said input measurement signals in accordance with the tool size offset desired direction to provide a tool size offset compensated end position signal, means for sequencing said combining means to combine respective significant digits of said BCD input code signals in sequential order, means for comparing said combined signals with the relative position measurement of said tool and workpiece from said reference position to cause said drive means to provide relative movement to the tool offset compensated end position, said sequencing means causing said combining means to combine the respective significant digits in sequential order from the most significant digit to the least significant digit; and wherein said combining means comprises a multi-bit shift register having a sufficient number of shift stages to store the tool size offset and end position measurements in straight binary code notation, a times 10 multiplier connected to the output of said shift register having output means and a two channel input full adder-subtractor circuit having its output connected to the inputs of said shift register; and wherein said sequencing means comprises first gate means for connecting the output of said shift register to one input of said adder, second gate means for connecting said multiplier output means to said adder-subtractor inputs, third and fourth gate means for connecting each of said measurement inputs to the other input of said adder, and an arithmetic cycle sequencer operative responsive to the input of each significant digit of said BCD code signals to sequentially:
 7. The control system of claim 6 wherein said comparing means comprises means for representing the relative positions of said tool and workpiece support in straight binary code notation signals and a full subtractor for comparing said position signals with the combined measurement signals, said driving means being responsive to the output of said subtractor to cause movement to the tool offset compensated end position.
 8. The control system of claim 7 wherein said driving means comprises separate motors for providing relative motion in at least two respectively perpendicular directions; and wherein said combining means comprises a second shift register, each register being associated with one of said directions and means for selecting at least one of said registers in accordance with the direction of travel to the compensated end position.
 9. For use with a machine having a tool rotatable about an axis, a workpiece support and driving means for providing relative movement between said tool and workpiece support, a control system for said driving means comprising input means for representing the radius of rotation measurement of said tool in BCD code notation signals, Input means for representing a desired relative end position measurement of the tool axis from a reference position in BCD code notation signals and for representing the desired direction of tool radius offset, means for arithmetically combining said input measurement signals, means for causing said combining means to add or subtract said input measurement signals in accordance with the desired direction of tool radius offset to provide a tool radius offset compensated end position signal, means for sequencing said combining means to combine respective significant digits of said BCD input code signals in sequential order, means for comparing said combined signals with the relative position of said tool and workpiece to cause said drive means to provide relative movement to the tool offset compensated end position, said sequencing means causing said combining means to combine the respective significant digits in sequential order from the most significant digit to the least significant digit; and wherein said combining means comprises a multi-bit shift register having a sufficient number of shift stages to store the tool offset and end position measurements in straight binary code notation, a multiplier connected to the output of said shift register having a times 2 and a times 8 output, and a two channel input full adder-subtractor circuit having its output connected to the inputs of said shift register; and wherein said sequencing means comprises a first gate for connecting the output of said shift register to one input of said adder, second and third gates for connecting each of said multiplier outputs to a respective one of said adder-subtractor inputs, fourth and fifth gates for connecting each of said measurement inputs to the other input of said adder-subtractor, and an arithmetic cycle sequencer operative responsive to the input of each significant digit of said BCD code signals to sequentially;
 10. The combination of claim 9 wherein said end position measurement and tool offset direction inputs comprise a punched tape reader and said tool offset measurement input comprises a manually controllable device.
 11. For use with a machine having a tool, workpiece support, and driving means to provide relative movement between said tool and workpiece support comprising means for arithmetically combining data inputs, means including a manual control for entering data relating to the actual amount plus or minus of work tool size offset required into said combining means, a prepared program input, means for entering data into said arithmetic combining means from said prepared program input relating to the actual desired dimension of the workpiece and to the required direction of tool size offset, means responsive to the entry of data relating to said required direction of tool size offset to cause said arithmetic combining means to add or subtract said data in accordance with the required direction of the tool size offset, and means responsive to said arithmetic combining means for causing said driving means to provide relative movement between said work tool and workpiece support in accordance with the desired dimension. 